Method and device for determining the thickness of foam

p00001Procedure and device to determine the density of a foam.

p00002The invention relates to a method for determining the density of a foam according to the preamble of claim 1, as well as to a device therefor, according to the preamble of claim 4.

p00003In beverage packaging facilities, especially when packaging carbonated beverages in beverage containers such as bottles, a foam layer is often produced. Depending on the type of beverage, more or less foam can be produced. Especially when packing beer, a lot of foam is often produced. Generally, it takes some time until the foam has precipitated, that is until the amount of bound liquid in the foam has dissolved. To control the amount of liquid in the beverage container, the filling level is measured. However, due to the foam formed, it is difficult or even impossible to carry out an exact determination of the level of filling immediately after filling, since this must wait until the foam has precipitated. The checking of the liquid bound in the foam, performed solely on the basis of the dimensions of the foam, generally yields erroneous results, since foam of different density is formed, so that the amount of bound liquid not only depends on the type of beverage , but also varies from one container to another.

p00004When packaging oxygen-sensitive beverages, such as beer, it is also common to inject just a thin ray of sterile water into the filler mouth (the so-called HDE procedure) just before the closer. The foam produced during this displaces the oxygen still present above the filling level. To check or control the correct operation, it would also be desirable to know something about the density of the foam produced.

p00005With usual procedures such as shortwave (HF), infrared deflection and infrared absorption it is not possible to determine the amount of liquid in the foam. These procedures have the disadvantage of not being able to detect different foam structures.

p00006WO2005 / 003758A1 describes a device for measuring the size of bubbles of a foam in a measuring vessel, for example a test tube, by lighting the foam with a strobe or the like and reproducing the foam by means of a CCD camera.

p00007Document DE102004054859A1 describes a procedure and a device for the optical control of foam in bottlenecks, in which the area of ​​the bottleneck, including the closure, is illuminated with an infrared light source and is reproduced backlight by means of a camera.

p00008EP0544428A1 describes a procedure and a device for assessing the foam quality of a beverage after packaging. To do this, the drink is poured into a glass cup, so that it can be illuminated laterally and reproduced through a camera. For this, a light source is proposed for the uniform illumination of the glass cup and its contents.

p00009Document DE102007004346A1 describes a device for the optical characterization of samples that are illuminated from several lateral directions, and optionally from above, and reproduced by a camera. For example, a lateral light source for producing light and a light source arranged approximately coaxially with the camera to produce incident light are described. In addition, a laser oriented obliquely with respect to the visual direction of the camera is described, so that after passing through the sample, the laser beam hits a screen where it can be reproduced by the camera.

p00010Although methods for measuring foam are known, only decomposition rates of the foams can be determined with them. In one of these procedures a beam of light is emitted to the foam and the light exiting the foam on the opposite side is recorded by a measuring device. The light beam and the measuring device rotate around the foam layer during the procedure. In addition, an exact determination of foam density is not possible with this procedure.

p00011Therefore, the object of the invention is to provide a method and a device with which the amount of liquid bound in the foam can be detected, for example to calculate the resulting filling level after the foam has been precipitated or to be able to monitor the foaming in general.

p00012The method for achieving this objective has the characteristics of claim 1. A light beam is irradiated to the foam produced immediately after introducing the liquid into the container or before the subsequent closure. Said ray of light enters the foam widening during it. To determine the density of foam, the contour of a point of light produced by the ray of light in the foam is determined, allowing the contour to draw conclusions about the density of foam.

p00013The procedure takes advantage of the effect that the foam causes a light beam to scatter. A density of foam of different heights causes different degrees of dispersion, that is, of widening of the beam. In a high density foam that binds a large amount of liquid, a strong dispersion of light rays occurs. On the contrary, the dispersion is less when the foam binds less liquid, that is, when the foam is less dense.

p00014The scattering of the light treated here is also called the Tyndall effect. This effect occurs when particles are suspended in a liquid or in a vessel, the size of the particles being comparable with the wavelength of the light (approx. 100 to 1,000 nm). The light is refracted in the particles, in this case, one or several bubble walls, and by this scattering of the light rays of light are dispersed that leave laterally from the medium. The dispersion makes the ray of light can also be seen from the side.

p00015In addition, the contour of the light point from outside the container is determined and compared with the stored data. Usually, foamy drinks are packaged in clear glass or plastic bottles. Therefore, the light beam that can be generated by a conventional laser in the market, especially focusing, in a power range of a few mw, can be directed to the foam from outside the container. Therefore, the measuring device that records the contour of the light point must also be disposed outside the bottle.

p00016To continue increasing the accuracy of the foam density determination, the foam density can be determined by several rays of light, especially light beams. It is known that the foam does not have a constant density along its length, so that in the case of a single measurement errors can occur. The light rays are irradiated to the foam in such a way that the originated light points do not cross and their contour can be clearly and clearly distinguished. Alternatively, pulsed lasers can also be used differently, with which overlapping points of light can also be detected and density can be determined from them.

p00017Additionally, the light points caused by the light rays are determined by at least one measuring device. The measuring device is also used to determine the foam height in a beverage bottle, so that it already records the total foam height. With a measuring device, depending on the orientation of the light rays it is possible to detect several points of light and determine the density in a corresponding area of ​​the light ray. However, several light rays can also be oriented in such a way that several measuring devices are required to record all the light points.

p00018By means of the amount of liquid in the foam, which can be detected in this way, the expected level of filling in the container or, in general, the quality or density of foam can therefore be determined.

p00019A device for achieving said objective has the characteristics of claim 4. According to it, the measuring device is configured in such a way that it can detect the contour of a point of light produced in the foam by the light beam. For this, the device has a light source and a measuring device arranged in the area of ​​the containers to be filled. The contour allows conclusions to be drawn about foam density, so the foam density can be determined with simple means.

p00020In addition, the device has a computer configured to calculate the amount of liquid bound in the foam, by comparing data of the contour of the point of light, stored, measured by the measuring device.

p00021According to an advantageous variant of the invention, the measuring device, especially a camera, is arranged laterally with respect to the light beam input, to measure the point of light from the side. The diffraction causes a dispersion of the light ray, whereby the light ray becomes visible laterally with respect to its longitudinal axis in the foam. Depending on the resulting scattered ray with respect to the foam density, the light spot varies in terms of its contour, size and light intensity on the foam. The contour of the light beam or the contour of the scattered ray can be easily recorded by the camera. Therefore, contour refers here to the decrease in light intensity starting from the center of the beam to both sides transversely with respect to the direction of the beam along the beam, as well as to the absolute values ​​of light intensity. In a simplified evaluation, it would be for example the relationship between the length and width of the contour of the scattered ray.

p00022According to another advantageous embodiment, it is provided that the light beam is generated by a preferably pulsed laser or a similar light source with focus. A laser emits a focused, focused beam of light, which during the measurement of the contour of the point of light allows to obtain a good result without further optical concentration.

p00023Advantageously, the laser can be activated at the camera frequency. In that way, it is possible to record not only individual images of the foam, but also several images in a row or a continuous image in the form of a film.

p00024According to another advantageous embodiment of the invention, several light sources and measuring devices are arranged laterally with respect to the container. Because of the density of the foam that varies even in a single foam formation, it is useful to measure several light sources so that different areas of the foam can be measured. In this case, advantageously, the light sources are arranged on top of each other along the height of the foam. Alternatively, the light sources can also be arranged in a plane, so that the foam is irradiated with a beam of light respectively from two or more sides. The camera, on the other hand, is usually configured in such a way that a larger area of ​​the foam is registered, which allows to register with a camera several light sources arranged one above and / or next to others, and the points of light generated by the same. For the exact determination of the contour of the points of light, several points of light recorded in an image are separated.

p00025The measuring device is arranged laterally and / or parallel with respect to the longitudinal axis of the light beam. Since the point of light exits the foam laterally with respect to the longitudinal axis of the light ray, the measuring device is arranged laterally with respect to the longitudinal axis of the light ray. It does not matter if it is arranged perpendicularly with respect to the beam of light. It should only be guaranteed that the measuring device records the point of light or the contour of the point of light constantly.

p00026According to a preferred variant, the computer comprises a memory in which data relating to the container and the liquid can be stored, especially the measurements and the thickness of the container material, preferably of the bottleneck, as well as the quality of the liquid. These data and information are determined before filling the containers and deposited in a memory. Because of the exogenous measurement, that is, from outside the container, a curvature and the thickness of the material of the wall of the container influence the measurement of the light spot, which by means of the corresponding prior storage can be taken into consideration in the determination of the result. Likewise, the volume of the foam layer can be determined through the measured height of the foam and the known volume of the container in this area. The computer presents an image processing software to determine the contour of the light spot. The data supplied by the camera is processed by image processing, so that the exact size of the light spot can be determined, for example in a surface unit. The same is true for the calculation of the foam height that is possible with image processing, as well as the quantity packed. Therefore, with image processing software it is possible to draw conclusions about foam density. In the case of overlapping light points or shots taken successively, these can also be evaluated with the help of image processing software.

p00027In addition, advantageously, it is possible to integrate the device into existing filling control devices per chamber. Therefore, existing camera systems, already installed for filling height control in packaging facilities, can be easily retrofitted with reduced expense.

p00028A preferable embodiment of the invention is described in detail below with the help of the drawing.

<dl><dt>They show: </dt><dd /></dl>

<dl><dt>Figure 1 </dt><dd>a side elevation of an upper area of ​​a beverage container with light sources </dd></dl>

<dl><dt>arranged laterally, </dt><dd /></dl>

<dl><dt>figure 2 </dt><dd>a top view of the beverage container with light sources arranged </dd></dl>

<dl><dt>laterally and with a measuring device, and </dt><dd /></dl>

<dl><dt>figure 3 </dt><dd>a schematic diagram to explain the invention. </dd></dl>

p00029An upper area of ​​a beverage container is shown in Figure 1. It is a drink bottle 10 with a bottleneck 11 that narrows conically. The bottleneck 11 flows into a thickened opening area 12. The beverage bottle 10 is a usual narrow neck bottle in the market, commonly used in the beverage industry, especially in the beer industry.

p00030In the illustrated embodiment, in the area of ​​the bottleneck 11, several light sources are arranged laterally in the form of lasers 13. Respectively two lasers 13 are in one plane. In total, six lasers 13 are arranged in three overlapping planes. In this manner, the bottleneck 11 is surrounded by lasers 13 at least in an area below the opening area 12, which are arranged along a longitudinal axis of the beverage bottle 12.

p00031Lasers 13 that are arranged in a plane are positioned with a displacement relative to each other in the contour. This means that the light beams 14 emitted respectively from the lasers 13 do not extend axially relative to each other. Rather, in the embodiment shown, its axes are in the corresponding plane with a displacement of approx. 120º with respect to others. An arrangement of two lasers 13 arranged in a plane can be seen in Figure 2.

p00032Figure 2 shows a plan view from above of the beverage bottle 10 with two lasers 13 arranged laterally. Additionally, a measuring device 15 is arranged in the form of a chamber, laterally with respect to the beverage bottle 10, in the plane of the two lasers 13. Generally, the measuring device 15 is positioned with respect to the beverage bottle 10 in such a way that it covers the entire area of ​​the bottleneck

p00033eleven. This means that the superimposed planes of the lasers 13 are recorded by a single measuring device 15. Therefore, to a measuring device 15 several lasers arranged parallel to each other are placed above and below each other. Alternatively, however, a measuring device 15 may also be assigned to each laser 13 or to a plane with lasers 13.

p00034In FIG. 2, a computer 16 is also shown, presenting a memory in which data relating to the beverage bottle 10 and the beverage may be stored. For example, data relating to the dimensions of the bottle 10, especially the bottleneck, and the wall thickness of the bottle are stored.

p0003510. Eventually, data related to the bottle itself can also be stored to allow, with the help of beverage characteristics, a more accurate interpolation or extrapolation over the entire height and, therefore, the development of a vertical density profile. The stored data can be based on empirical values, experiments or previous measurements. In addition, the computer features image processing software. The contour of the light spot 17a, 17b can be determined by image processing.

p00036Next, the process according to the invention is described in detail with the aid of Figure 3: The foam layer caused during filling in the area of ​​the bottleneck 11 contains an amount of liquid which, once the foam, makes the level rise in the bottle of drink 10. In order to be able to evaluate, immediately after filling, how much liquid is bound in the foam, with a laser 13 arranged laterally, a ray of some! Sec is irradiated to the foam. a few msec., which produces in the foam the point of light 17a or 17b that can be seen from the side and which according to the density has a different contour. The contour of said point of light is recorded with the camera 15 positioned laterally with respect to the direction of the beam and, then, from the measurement result the amount of liquid is determined, for example by comparison with the previously recorded data.

p00037Usually, the measuring device 15 is conceived in such a way that, in addition to registering the light spots, it is also capable of also determining the height of the foam layer. In this way, it is additionally possible to include, in order to determine the foam density, several lasers arranged along the longitudinal extension of the beverage bottle 10. Therefore, with a measuring device 15 a greater number of points of light projected on the foam. From the vertical foam density profile and the foam height, knowing the inside diameter, the amount of liquid stored in the foam can be calculated by integration.

p00038Generally, it is sufficient to determine the foam density and therefore the amount of liquid bound with a single measurement procedure. A measurement procedure corresponds to an image of the camera. The laser (s) are activated in such a way that their frequency corresponds to the recording time of the camera. Alternatively, several images of light spots can also be created, for example to determine the temporal course of foam precipitation.

p00039In another application of the invention, the system according to the invention is used as a control system in combination with an HDE process during the packaging of oxygen-sensitive beverages, to monitor whether sufficient foam has been produced to expel residual oxygen through the opening. from the mouth

p00040The device can be easily integrated into existing filling height control devices. Since at present, the filling height control is usually already carried out with a camera system, the invention can be easily carried out, because the existing system must only be complemented with the laser (s) and suitable image processing software .